新型医用低模量钛合金及其表面含Ag纳米管的制备和生物学基础研究

The instability at the implant-bone interface is one of the main reason during the failure of joint arthroplasty. The mechanisms are including①unsatisfied osseointegaration②the bacterial adhesion is the most important procedure ③One of the main reason is the stress shielding effect at the implant-bone interface resulting from the higher elastic modulus of Ti-6Al-4V (110GPa) relative to that of natural bone(30 GPa).Therefore, we are focus on how to fabricate a new titanium alloy with low modulus and antibacterial properties.Our preliminary experiment showed that the biocompatibility of a novel titanium alloy Ti35Nb3Zr2Ta with lower elastic modulus (48GPa) is much better than that of Ti6Al4V , which is widely used in orthopedics. Silver (Ag) is one of the strong bactericides and has attracted increasing attention because of many benefits such as a broad antibacterial spectrum including antibiotic-resistant bacteria, non-cytotoxicity at suitable doses, satisfactory stability, and smaller possibility to develop resistant strains. According to these, a novel nanotube with Ag was fabricated on the surface of the Ti35Nb3Zr2Ta through anodic oxidation. The present in vitro and vivo study aims to evaluate the biocompatibility and the antibacterial properties of the novel nano- Ti35Nb3Zr2Ta. The initial adhesion and subsequent proliferation of S. epidermidis and osteoblasts were visualized both by SEM and confocal laser scanning microscopy (CLSM). In addition, differentiation and calcium depositon of osteoblasts were also studied by real time PCR.

人工关节假体骨-金属界面固定失去稳定可导致手术失败，其发生机制包括①假体表面骨整合不良②细菌早期粘附到假体表面引起关节感染③假体材料与骨骼弹性模量不匹配。因此，亟待研发具有低弹性模量、高骨整合度及早期抗菌性特点的钛合金材料。本课题组自主研发新型低模量钛合金Ti35Nb3Zr2Ta（48GPa），预实验已证实其明显促进成骨细胞增殖、分化及骨生成。本课题拟研究在该材料表面原位生长纳米管增加骨整合性，纳米管合成时掺入Ag+杀灭细菌。体外将材料与成骨细胞、金黄色葡萄球菌共培养，体内将材料植入动物髓腔内，采用PCR检测成骨相关基因，硬组织切片及MicroCT检测材料表面骨长入等手段，从分子及细胞学等多方面探讨该新型材料的骨整合性及抗菌性能。本实验为研发具有低模量、高骨整合度及预防人工关节感染特点的新型国产化假体奠定理论基础。

本课题以我们制备出具有自主专利的Ti35Nb2Ta3Zr合金为研究对象，（1）通过与成骨细胞的培养，及植入兔体内，研究Ti35Nb2Ta3Zr的生物相容性。（2）在Ti35Nb2Ta3Zr合金表面引入含银纳米管涂层，通过离子释放实验，体外抗菌实验以及细胞相容性实验探究其最佳抗菌浓度。（3）在Ti35Nb2Ta3Zr合金表面引入含锶钙磷涂层，通过体外与成骨细胞共培养，以及体内动物实验，研究其体内外促成骨作用。通过研究我们得出下列结论： 1．Ti35Nb2Ta3Zr在模拟体液中的抗腐蚀性能和体内外生物相容性与TiTi6Al4V合金相当，表明添加元素铌、钽、锆元素后，一方面达到了降低弹性模量到与人体骨弹性模量相一致的目的，又不影响其腐蚀性能和生物相容性； 2．基于阳极氧化，以AgNO3为缓冲液，在Ti35Nb2Ta3Zr表面能够形成含有不同Ag+浓度的纳米管涂层，体外抗菌实验和细胞毒性实验表明表面银离子浓度增高有利于提高其抗菌性能，但也会产生一定的细胞毒性，因此，引入适量的银离子浓度（NT-Ag1.0），既能够保证其良好的生物相容性，也能够使其具有一定的抗菌性能。3．基于微弧氧化，以Sr(CH3COO)2为缓冲液，在Ti35Nb2Ta3Zr表面既能够生成多孔结构，又能引入具有促进成骨作用的微量元素锶。体内外实验结果表明含锶钙磷涂层能够促进合金的体内外成骨作用，增加骨-假体间的骨整合。总之，该研究为Ti35Nb2Ta3Zr合金从基础研究向临床应用转化提供实验依据及支持。

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